Revert of Raise exception when devices fail to list tests.

build/android/pylib/local/device/local_device_gtest_run.py

Index: build/android/pylib/local/device/local_device_gtest_run.py
diff --git a/build/android/pylib/local/device/local_device_gtest_run.py b/build/android/pylib/local/device/local_device_gtest_run.py
index a723cfe6726fdb48ec414402d70bcfa0f49687a3..cb8dc471521d7c7e58fee0918195f2dfa7d2784c 100644
--- a/build/android/pylib/local/device/local_device_gtest_run.py
+++ b/build/android/pylib/local/device/local_device_gtest_run.py
@@ -321,8 +321,7 @@
     test_lists = self._env.parallel_devices.pMap(list_tests).pGet(None)
 
     # If all devices failed to list tests, raise an exception.
-    # Check that tl is not None and is not empty.
-    if all(not tl for tl in test_lists):
+    if all([tl is None for tl in test_lists]):
       raise device_errors.CommandFailedError(
           'Failed to list tests on any device')
     return list(sorted(set().union(*[set(tl) for tl in test_lists if tl])))